1. Field of the Invention
The invention pertains to a large mobile crane with an undercarriage, a drive unit, a superstructure, one or more control stations, at least two main booms, at least one derrick boom, at least two lifting devices and counterweights, either separate or mounted on the basic machine.
2. Description of the Related Art
Various solutions are known for lifting extremely heavy loads exceeding the capacity of the various current mobile crane designs, large numbers of which are on the market.
It is possible, for example, with the use of the reliable mechanical elements and materials already available for constructing cranes, to build a very large lattice-boom crawler crane whenever desired. As a result of the necessary size of the individual components, however, considerable problems are encountered in the production of the castings in particular, such as the base plates and cable drums as well as the hydraulic components. Although technological limits are reached in some cases, economic limits are reached in all cases, and all of the large cranes thus obtained would include individual pieces difficult to move from one work location to another. The large components present significant problems with respect to transport and handling such as the ability to be driven along ordinary roads and to pass under bridges. An alternative solution, namely, dividing the individual basic components into smaller components, would lead to additional, relatively high costs. Overall, a large machine of this type would be extremely expensive and, as experience has shown, would represent a commercial prototype.
Ring-lift cranes represent a different approach to the lifting of heavy loads. These usually have a large boom or a double-boom system (arranged in parallel or in the shape of an “A”), which are supported on the ground by way of a circular track. In the meantime, several patents have been granted for cranes of this type such as U.S. Pat. Nos. 4,103 783 and 4,196 816. The advantage of the ring-lift crane is that much higher load moments can be reached than is possible with crawler cranes. The disadvantage is that ring-lift cranes cannot be moved with a suspended load, and even without a load they can be moved only with considerable effort. In addition, they can make use of only a few components of standard production cranes. They must therefore usually be assembled on site and thus block the progress of the construction work during the tedious assembly and disassembly phases.
So-called derrick cranes are also known. Here a main boom is paired with a derrick boom, the two booms being mounted on the superstructure of a mobile undercarriage or on a stationary foundation.
The extremely large dimensions of all these machines, as previously mentioned, is disadvantageous, because they cause problems during transport and assembly/disassembly. They also suffer from poor lateral stability (especially serious in the case of loads with large surface areas exposed to the wind) because of the unfavorable relationship between the large size of the machine and the short distance between the tracks of the crawler-type carriage.
It is therefore the task of the present invention to eliminate the disadvantages of the known solutions and thus to lower the investment cost for the task-optimized design and installation of large cranes of any desired type and with any desired set of properties.
According to the invention, wherein the components of the crane which absorb the load and the components which provide mobility are designed in modular fashion and can be replaced and supplemented with expansion parts, where the structural units (modules) used essentially correspond to, or resemble, existing standard crane components, and where multiple modules can be combined to form a large crane with a greater working load capacity.
The invention is based on the core idea of creating a mobile crane which is variable, that is, a crane which can be built to suit a specific need. This is accomplished essentially in that, as far as possible, components of existing standard production cranes are used in favorable combinations with expansion parts in a wide variety of ways to achieve large and very large crane configurations.
According to an especially advantageous embodiment, a crane of the derrick type has a double main boom arrangement and a double derrick boom arrangement. The two adjacent booms of a pair are connected to each other preferably so that they are rigid with respect to moments. As a result of this arrangement, the load capacity is significantly increased without limiting the mobility of the basic machine.
Standard components are used as often as possible to build the various configurations of the crane. This applies not only to the load-bearing components but also to the parts which provide the mobility. Thus, for example, through the modular design of the crawler-type carriage or crawler carrier, the footprint can be easily and quickly increased, for which purpose standard components can also be used.
The ability to change the working load possibilities can be improved even more by simplifying the way in which the counterweight being used can be adapted to the load. In other words, it should be possible without major effort to adapt the counterweight to heavier loads as well as to reduce it so that the desired variability can be achieved. This is accomplished by dividing the counterweight into a mobile component and a stationary component. This separation is the object of modular counterweight carriage disclosed in WO 2007/056970.